1. Technical Field
The invention relates to air springs, and more particularly to an improved sleeve used therein. Even more particularly, the invention relates to an air spring sleeve having modified ends which reduce slippage from beneath the clamp ring without effecting the ride characteristic of the air spring.
2. Background Information
Air springs typically include two end members which are sealingly connected to respective ends of a fabric reinforced flexible bladder or sleeve. These air springs are used primarily for implementation in motor vehicles, supporting the vehicle body, or for use in other types of equipment subject to shock to provide cushioning therefor. The air spring sleeve usually has opposed open ends which are sealed to the end members by a clamp or swage ring to form a pressurized fluid chamber within the sleeve. The flexible sleeve usually consists of inner and outer layers of a non-reinforced elastomeric material with a plurality of reinforcing schemes sandwiched between these inner and outer layers or combinations therein. The modulus of the elastomeric material must be low enough to continuously flex as the air spring moves from extended to compressed positions without deteriorating to provide a durable air spring. However, the low modulus material, although satisfactory for retaining the pressurized fluid within the air chamber and for providing sufficient durability, increases the difficulty of forming an airtight seal with the end members, which is usually accomplished by a swage or clamp ring. The swage ring clamps the intervening sleeve ends against a clamping surface formed on the end member with the ring and/or the end members having various projections and grooves to enhance clamping effectiveness. The use of this low modulus material can cause slippage from beneath the swage ring or excessive wrinkling, resulting in potentially too restrictive leakage paths being created between the internal fluid chamber and surrounding atmosphere.
Prior art air spring sleeves have attempted to overcome this problem by increasing the hardness of the sleeve ends, such as shown in U.S. Pat. No. 3,319,952. However, this sleeve construction, as well as other prior art sleeve constructions having reinforced ends, increase the thickness of the sleeve ends in order to achieve the increased hardness and reduce slippage. These thickened ends can increase the manufacturing costs and can require use of different assembly machines and crimping machines than those used with elastomeric sleeves which have a uniform thickness throughout their axial lengths.
Thus it is desirable to form the flexible sleeve for an air spring having ends formed of a material with a higher modulus of elasticity than the majority of the sleeve material in order to increase the stiffness in the clamped area without materially effecting the flexibility and durability of the elastomeric sleeve. Generally, the higher the modules of elasticity, the harder the sleeve material as applied to rubber products; that is, hardness becoming the relative resistance of the surface to indentation as measured by normal means.
One aspect of the present invention is to provide an elastomeric sleeve for use in an air spring in which the ends of the sleeve have a higher modulus, and thus stiffer material to provide a more effective sealing engagement when clamped between a swage ring and sealing surface of the end member, and which will not effect the ride characteristic of the air spring and durability thereof, by enabling the lower modulus elastomeric material to be used throughout the majority of the axial length of the sleeve.
A further feature of the invention is to provide a flexible sleeve with a uniform thickness throughout its entire axial length, thereby enabling existing air spring assembly equipment and tooling to be utilized.
The sleeve of the present invention enables the sleeve to be formed of an elastomeric material which contains one or more plies of reinforcing material to extend throughout its axial length as in prior art sleeve constructions having the same or similar elastomeric material layers extending completely through the sleeve length.
In one of the embodiments of the invention, only the inner layer of the modified end portion of the sleeve is formed of a higher modulus material, and in another embodiment, only the outer layer of the end portion is formed of the higher modulus material; and in a further embodiment, both the inner and outer layers of the modified end portions of the sleeve are formed of the higher modulus material.
In accordance with one of the main aspects of the invention, the higher modulus layers in the end portions of the sleeve are joined with the lower modulus inner and outer layers of the sleeve by a non-overlapping joint, such as a butt joint or bevel joint, so as not to effect the overall uniform constant thickness of the sleeve.
Preferably, the Shore A harness of the end portion or portions of the sleeve, which can be correlated to the modulus of elasticity, will be at least 45 to 50.